Bag and method of forming same



Jan.'2, R. R. GOINS BAG AND METHOD OF FORMING SAME Filed May 27, 1966 2 Sheets-Sheet 1 INVENTOR R.R.GOINS A T TORNEYS Jan; 2, 1968 R. R. GOINS 3,361,335

BAG AND METHOD OF FORMING SAME Filed May 27, 19 66 2 Sheets-'Shet 2 INVENTOR RVRGOINS A T TOR/V5 VS United States Patent Ofiice 51361335 Patented Jan. 2, 1968 3,361,335 BAG AND METHOD OF FORMING SAME Robert R. Goins, Bartlesville, Olden, assignor to Phillips Petroleum Company, a corporation of Delaware Filed May 27, 1966, Ser. No. 553,505 12 Claims. (Cl. 22958) This invention relates to closed-end bags made from tubular stock and a method of forming closed ends thereon.

Bags for storing and transportation of numerous solid particulate materials, such as cement, fertilizers, poly mers, resins, carbon black, catalyst powders, etc., are conventionally formed with a closed bottom and a closed top with a gusseted valve for filling the bag. Such bags are usually made from tubular material by folding the ends of a tube of said material of a selected length to form the closures. One problem in bags made by this method lies in weakness near the corners of the closure. Another problem with certain bags lies in the formation of small openings at the bag corners for leakage in or out but which leaves a weak spot where a tear can readily start.

This invention is concerned with a method of closing the ends of a relatively thin, flexible tube made of a suitable bag material in such a manner that the foregoing problems are avoided.

Accordingly, it is an object of the invention to provide an improved method for forming a bottom on the end of a tubular piece of bag material from the walls of the tube itself which results in an improved bag. Another object is to provide a method of forming a top closure on a tubular bag which forms a valve gusset and provides a strong closure resistant to tearing. A further object is to provide a bag formed of tubular material which has a strong bottom closure formed of sections of the bag wall. A further object is to provide a bag having an improved top closure having a gusseted filling valve. A further object is to provide an improved tubular bag having top and bottom closures made of sections of the bag Wall with provision in the top closure for filling valve means and controllable leakage means in the bottom closure for use in filling. It is also an object of the invention to provide a method for locating slits in a tube for folding the end of the tube into a closure for a bag. Other objects of the invention will become apparent to one skilled in the art upon consideration of the accompanying disclosure.

In accordance with the invention, utilizing a length of flexible, thin-walled tube to form a bag, the plane of the closure (bottom or top) of the bag is determined or defined by spacing same from the end of the bag a distance greater than one-half and less than the full width of the closure and a rectangular periphery for said bottom; cutting two pairs of longitudinal slits in the tube extending from the adjacent end of the tube to said plane to form a pair of opposite end flaps and a pair of opposite side flaps, the slits being offset from the corners of the closure to space the side flaps therefrom; infolding the side flaps along the periphery of the closure intothe plane thereof and sealing these to each other along their overlapping section; infolding the end flaps along the periphery of the closure into the plane thereof so as to overlap the folded side flaps and sealing same to the resulting overlapped side flaps, leaving relatively narrow strips or auxiliary flaps along opposite sides of each end flap extending from the wall of the tube along the plane of the bottom; and folding each such strip or auxiliary flap onto the adjacent wall of the tube, sealing same thereto, and simultaneously folding under a small section of each strip or auxiliary flap at the adjacent corner of said closure. The foregoing procedure is applied in forming a bottom closure on a tubular bag which provides a small amount of leakage for air when filling the bag.

Leakage is provided at the bottom corners of the bag by sealing only the long edges of the auxiliary flaps and not the short edge opposite the infolded edge. This leakage provided along the underside of the auxiliary flaps and between same and the adjacent bag wall near the bottom can be controlled by varying the width of the seal between the auxiliary flaps and the adjacent bag wall. The three-walled construction at the corners of the bag provides desirable reinforcing in this area.

When forming the top closure of the tubular bag, a different series of folding steps is followed. The bag is slit in the same manner as when forming a bottom closure but one of the end flaps is infolded first and the auxiliary flaps along the edges thereof adjacent the sides of the bottom are folded and positioned inside of the tube and sealed to the inner wall thereof. The two side flaps are next infolded so as to overlap and sealed at their overlapping portions but not sealed to the first infolded end flap so as to provide an entry fora filling spout to be used in filling the bag. The other end flap is then infolded to overlap the sealed side flaps and the auxiliary flaps are folded along and sealed to the outside Wall of the tube.

A more complete understanding of the invention may be had by reference to the accompanying schematic drawing of which FIGURE 1 is a plan view of a lay-flat tube of bag material provided with longitudinal slits for folding; FIGURES 2, 3, and 4 are pictorial views of the bottom end of a bag at different stages of folding; FIGURES 5, 6, and 7 are pictorial views of the top end of a bag at different stages of folding; and FIGURE 8 is a plan view of a completed bag in flattened condition for packaging and shipping.

Referring to FIGURE 1, a flattened tube 19 made of any suitable thin, flexible bag material, such as polyethylene, heavy paper, metal foil, particularly recently developed steel foil, etc., is slit or cut inwardly from each end to provide slits 12. The resulting tube is then foldable in the manner illustrated in the remaining figures to provide a bottom closure and/or a top closure. Dotted lines 13 designate fold lines along the bottom and top of the bag while dotted lines 14 indicate the fold lines in the end flaps to provide auxiliary flaps which will be more clearly seen in the following figures. To illustrate, assuming the flattened tube is 18 /2 inches wide and a rectangular bottom 5" 13 A2" is desired as the configuration of the bag, cuts 12 are positioned three inches inside the edges of the bag, parallel with the edges, and extend three inches in from the tube end. This three-inch spacing from the edges of the top allows the end flaps 16 to extend around the corner of the bag and to side flaps 18. Thus, the cut end flaps are 6 inches Wide and one inch wider than the 5-inch width of the bottom to be formed. The length of the slits (3 inches) must be more than one-half of the width of the bottom and not greater than the full bottom width to provide for overlap of the side flaps without extending outside of the bottom. Steel foil is particularly strong and is well adapted to formation of bags in accordance with the invention. Welding at the sealing areas is feasible. It is also feasible to coat the steel foil with a thin coat of polyethylene or other thermoplastic and bond the sealing areas with heat as in sealing plastic sheet.

Referring to FIGURE 2., which illustrates the bottom end of a bag after the first folding step, side flaps 18 are shown infolded along with overlapped bottom edge 20 of the first folded side flap and exposed edge 22 of the second folded side flap. The overlapping section is sealed in conventional manner, using heat sealing for plastic bags and glue sealing for other types of bags which absorb glue. End flaps 1d are not folded and extend around the corner of the bag to the side flaps. The extending portion 24 forms the auxiliary flaps along each side of the end flaps for scaling to the sides of the bag after infolding of the end flap. Dotted lines 26 are fold lines which will become peripheries of the bag bottom.

Referring to FIGURE 3, the first end flap 16 has been infolded to overlap the side flap and auxiliary flaps 24 extend outwardly beyond the periphery of the bottom and are readily foldable along the outside wall of the tube or bag to form reinforcement of the bag or bottom.

FIGURE 4 shows both end flaps infolded and the auxiliary flaps 24 folded along the bottom line and onto the outside wall of the bag. When folding flaps 24 there must be an infold or underfold made in the flap adjacent the corner of the bag as indicated at 28. This provides three thicknesses of bag material in this triangular area for reinforcing the corner and provides a controlled leakage for ingress and egress of air during filling and emptying of the bag Auxiliary flaps 24 are sealed to the wall of the bag along a strip adjacent the outermost edge but not along a narrow strip adjacent their juncture with the bottom to provide controlled leakage under these flaps.

In some instances it may be desirable to seal an extension onto the fiap 16 which goes under side flaps 18 to form the filling valve 34 as in FIGURES 5 thru 8. This extension may be formed of more flexible material than the bag material to aid in sealing after filling.

FIGURES 5, 6, and 7 show the procedure for folding the end and side flaps to form a top closure. In FIG- URE 5, the first end flap 16 has been infolded and the auxiliary flaps 24 have been infolded along the inner wall of the bag and sealed thereto. In this figure, the near side flap 18 is partially cut away to better show the first folding step. In FIGURE 6, side flaps 18 have been folded so as to overlap and are sealed along the overlap but not sealed to the first-folded end flap 16. The next step involves infolding the second end flap 16 with auxiliary flaps 24 extending along the outside wall of the bag and sealing the end flap to the overlapped side flaps and the auxiliary flaps to the bag wall by conventional sealing means, as shown in FIGURE 7.

In FIGURE 8, the folded ends of the bag are turned to the same side of tube 10 which is folded flat. The bottom, designated 30, shows end flaps 16 overlapping side flaps 18. The top closure, designated 32, shows the edge 34 of the filling valve formed by first infolding end flap 16 and then infolding side flaps 18, followed by sealing the overlapped sections of the side flaps but not sealing the side flaps to the first infolded end flap. The second infolded end fiap then overlaps the side flaps and is sealed thereto.

Certain modifications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

I claim:

1. A method of forming a bag from a length of flexible thin-walled tube having a square end by providing a rectangular bottom on said end which comprises the steps of:

(l) defining the plane of said bottom parallel with said end and spaced therefrom a distance greater than /2 and less than the full width of said bottom and a rectangular periphery for said bottom;

(2) cutting 2 pairs of longitudinal slits in said tube extending from said end to said plane to form an opposite pair of rectangular side flaps which overlap when folded inwardly along said plane and a pair of rectangular end flaps which extend around the corners of said bottom and along the sides thereof;

(3) folding said side flaps along the periphery of said bottom inwardly into said plane and sealing same to each other along their overlapping section;

(4) infolding said end flaps along the periphery of said bottom into said plane so as to overlap the folded side flaps of step (3) and sealing same to the resulting overlapped side flaps, leaving relatively narrow auxiliary flaps along opposite sides of each side flap extending outwardly from the wall of said tube along the plane of said bottom; and

(5) infolding each said auxiliary flap at the side periphery of said bottom onto the adjacent wall of said tube and sealing same thereto, simultaneously folding under a small section of the end of each said auxiliary flap at the adjacent corner of said bottom.

2. The method of claim 1 wherein each said slit is located by the steps of:

(l) flattening said tube to form a double-walled sheet, the side edges representing the centers of the bag sides to which the end flaps are attached;

(2) measuring in from each side edge parallel with said end to a point a distance substantially greater than /2 the width of said bottom and not greater than the full width thereof; and

(3) running a line thru each said point parallel with said edge from said end to a point a distance from said end substantially the same as the distance of step (2).

3. The method of claim 1 including forming a top closure on said bag generally parallel with said bottom which comprises the steps of:

(6) defining and forming slits in the top of said bag substantially as in steps (1) and (2); V a

(7) folding one resulting end flap along the periphery of said top inwardly along said top with its overlapping auxiliary fiaps extending inside of said bagalong the adjacent side walls thereof and sealing said auxiliary fiaps to said side walls;

(8) folding and sealing said side flaps as in step (3) but not to the end flap of step (7) so as to leave a filling valve; and

(9) folding and sealing the remaining end flap and its auxiliary flaps along the edgesthereof as in step (4).

4. The method of claim 3 including the step of sealing a reinforcing strip on the outside of said top substantially coextensive therewith.

5. The method of claim 1 using as said tube a lay-flat tube of flexible sheet, including sealing said auxiliary flaps of step (4) to the bag wall only along their long edges to provide a controlled breathing vent.

6. A bag comprising:

(a) a tubular wall;

(b) a rectangular bottom formed of:

(1) side flaps of oppositely infolded portions of said tubular wall overlapping and sealed to each other, said side flaps being narrower along their folds than the corresponding edge of said bottom so as to be spaced from the adjacent bottom corners but covering a major portion of said bottom;

(2) end flaps of oppositely infolded remaining portions of said tubular wall overlapping and sealed to the infolded side flaps of (1) and providing a narrow auxiliary flap along each outer edge of each end flap, each said auxiliary flap extending along and being sealed to the adjacent bag wall and being tucked under adjacent the corner of said bottom to form 3 layers of wall in the tuck area.

7. The bag of claim 6 formed of. tubular resin or plastic film heat sealed in the sealed areas.

8. The bag of claim 6 further including:

(c) a rectangular top closure formed of (1) a first end flap comprising an infolded portion of said tubular wall having a narrow auxiliary flap extending from each side edge along the inside wall of said tube and sealed thereto holding said end flap in the plane of said closure;

(2) side flaps comprising oppositely infolded portions of said tubular wall overlapping and sealed J to each other but not to the end flap of (c) (1) thereby providing a filling valve between said first end flap and the overlapping side flaps,'said (3) a second end flap comprising an infolded portion of said tubular Wall overlapping and sealed to said side flaps, said second end flap having narrow sections corresponding to those of said first end flap of (c) 1) overlapping and sealed to the outside Wall of said tube.

9. The bag of claim 8 including a reinforcing strip overlapping and sealed to said second end flap of (c) (3) and the exposed sections of said side flaps but not to said first end flap of (c)(1).

10. A tubular bag having a rectangular top closure comprising:

(a) a first end flap formed of an infolded portion of said tubular bag wider than the corresponding end of said bottom and extending around the adjacent sides thereof thereby providing narrow additional flaps which overlap and are sealed to the adjacent inner wall of said bag, the corner of each said additional flaps adjacent the corresponding corner of said top being folded under to provide a reinforced 3-walled section;

(b) side flaps formed of oppositely infolded portions of said tubular bag overlapping and sealed to each other,

3,140,809 3,277,798 10/1966 Krauss 22957 said side flaps being narrower than the edge of said top along the adjacent fold; and

(c) a second end flap formed of an infolded portion of said tubular bag similar to the first end flap of (a) but with said additional flaps overlapping and sealed to the outside wall of said bag, the corners of said additional flaps adjacent the corners of said top being folded under and providing a reinforced 3-Wa11ed section.

11. The bag of claim 6 formed of tubular steel foil heat sealed in the sealed areas.

12. The bag of claim 6 wherein said auxiliary flaps are References Cited UNITED STATES PATENTS 7/ 1964 Hickin et a1 229-37 JOSEPH R. LECLAIR, Primary Examiner. 25 R. PESHOCK, Assistant Examiner. 

6. A BAG COMPRISING: (A) A TUBULAR WALL; (B) A RECTANGULAR BOTTOM FORMED OF: (1) SIDE FLAPS OF OPPOSITELY INFOLDED PORTIONS OF SAID TUBULAR WALL OVERLAPPING AND SEALED TO EACH OTHER, SAID SIDE FLAPS BEING NARROWER ALONG THEIR FOLDS THAN THE CORRESPONDING EDGE OF SAID BOTTOM SO AS TO BE SPACED FROM THE ADJACENT BOTTOM CORNERS BUT COVERING A MAJOR PORTION OF SAID BOTTOM; (2) END FLAPS OF OPPOSITELY INFOLDED REMAINING PORTIONS OF SAID TUBULAR WALL OVERLAPPING AND SEALED TO THE INFOLDED SIDE FLAPS OF (1) AND PROVIDING 